Various types of joint assemblies are utilized to interconnect HVAC ducting of circular, oval, square, rectangular, or other cross-sectional shapes. One type of joint assembly is in the form of a flanged ring, which is connected to the end of a duct section to present a mating flange extending transversely to the length of the duct and extending radially or laterally from the exterior of the duct. The two mating flanges of the adjacent flanged rings may be attached together in face-to-face relationship by screws, bolts, or other hardware members extending through the mating flanges, as well as connector rings or clips that entirely or partially encircle the exterior of the mating flanges of the adjacent flanged rings.
It is often necessary to place a gasket between the two mating flanges of the adjacent flanged rings to control or avoid leakage of air or other gases being transmitted through the ducting. Ensuring that the gasket is properly assembled with the flanged rings has been challenging. It is possible to glue a gasket to one or both of the mating flanged rings. However, additional labor is required to glue the gasket to the mating flange. In addition, during transport or assembly the gasket material may become damaged or become detached from the mating flange.
Also, in large-diameter HVAC ducting, the flanged rings are often not sufficiently stiff to create a satisfactory joint between the HVAC duct sections. The flanged rings can be manufactured from thicker gauge material, but doing so increases the cost of the flanged rings, and increases the weight of the flanged rings, as well as increasing the difficulty in forming the flanged rings into desired shapes. As such, efforts have been made to produce flanged rings with exterior hems and returns to increase the section modulus of the flanged rings. However, other alternatives for reinforcing or increasing the strength and rigidity of flanged rings are desirable.